Oligoastrocytoma NOS

Case contributed by A.Prof Frank Gaillard
Modality: MRI

A region of high T2 signal involving the cortex of right paracentral lobule has minor mass effect and no enhancement. 

Case Discussion

The patient went on to have a resection. 

Histology

Microscopic Description: 

Sections show seven fragments of grey and white matter, three of which are completely replaced by tumour, whereas two are partially infiltrated by tumour at one end. The tumour is a diffusely infiltrating, densely cellular glial neoplasm composed of a mixture of two distinct neoplastic cell types with morphologic features of oligodendrocytes and astrocytes. For the most part, the two components are diffusely admixed, whereas one of the smaller fragments is composed almost entirely of neoplastic astrocytes. The oligodendroglial component consists of small cells with round nuclei and perinuclear halos and includes scattered microgemistocytes. The astrocytic component consists of tumour cells with GFAP-positive cytoplasm drawn out into processes. There is mild nuclear pleomorphism and a small number of scattered mitotic figures. In the most cellular fragment of the tumour there is prominent satellitosis of cortical neurons by tumour cells.The MIB-1 staining shows scattered cells in mitotic cycle as indicated by the positive nuclear staining. There is no necrosis. A single microvessel shows slightly prominent endothelial cells, however, there is no overt vascular endothelial proliferation The remaining two fragments of white matter are free of tumour.

Final Diagnosis: 

Diffusely infiltrating glial neoplasm with features of oligoastrocytoma

NOTE: This case predates the 2016 WHO classification of CNS tumour revision. As no 1p19q co-deletion status is available a formal diagnosis cannot be reached and the NOS is therefore used (not otherwise specified) - which is recognised in the current classification for cases where molecular information is unavailable. It should also be noted, that under the new classification both an astrocytic and oligodendroglial component needs to be identified, each with its own molecular markers. True oligoastrocytomas are therefore going to be rare, and this case would most likely be classified as either an astrocytoma or an oligodendroglioma. 

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Case Information

rID: 5268
Case created: 29th Dec 2008
Last edited: 21st Dec 2016
Inclusion in quiz mode: Included

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